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observation of the cuttings removed from the trench and the action of the excavating tools on the bedrock <br />surface. <br />3.13 SLURRY AND BACKFILL <br />Testing requirements for slurry and backfill are as follows (and are outlined in Table 1): <br />A. Materials <br />1. Bentonite: Certification of compliance with the specifications shall be obtained from the <br />material manufacturer. <br />2. Backfill Mix: Backfill material shall be tested prior to placement in the trench by <br />conducting tests to determine slump and gradation. Testing frequency will be as directed <br />by the Engineer with a minimum of one slump test per 100 cubic yards and one gradation <br />per 300 cubic yards of backfill material prepared for introduction in the trench. <br />B. Slurry Introduced in the Trench <br />A complete series of tests shall be conducted on slurry from the pond containing slurry ready for <br />introduction in the trench each time a pond is prepared. On a daily basis viscosity and unit weight <br />tests will be performed twice per shift. Filtrate loss and pH tests will be performed once per shift. <br />The complete series of tests shall include: <br />- pH of the slurry, <br />- Unit weight of the slurry, <br />- Viscosity of the slurry, <br />- Filtrate loss of the slurry. <br />C. Slurry in the Trench <br />Slurry in the trench shall be tested for viscosity and unit weight at least twice per shift and sand <br />content and filtrate loss at least once per shift. Samples shall be obtained from near the bottom of <br />the trench near the point of trenching. <br />3.14 SOUNDINGS <br />Soundings shall be taken every 20 feet along the trench centerline using a weighted tape, cable, or other <br />device. Soundings shall be recorded to the nearest 0.5 feet. Soundings shall record the following <br />information: <br />A. Top of Key Depth: The top elevation of the key taken after the determination of key is made from <br />observation of cuttings produced during the excavation. <br />B. Bottom of Excavation: The elevation of the bottom of the trench after the complete excavation of <br />the key material subject to approval by the Engineer. <br />C. Bottom of Excavation Prior to Backfilling: Soundings shall be used to monitor for sidewall <br />collapse and sediment accumulation along the trench bottom before the beginning of backfilling. <br />D. Profile of Backfill Slope: The S -B backfill slope and trench bottom shall be sounded at the <br />beginning and end of every shift. This information can be used as an indicator of trench collapse, <br />excessive settlement, or sloughing. <br />Wattenberg Resource Pond 3 Slurry Wall Section 02168 — Slurry Wall Construction <br />Page 5 <br />